Abstract: A cylinder head with which exhaust manifolds are integrated includes a secondary air supply passage configured to include: a main passage disposed above combustion chambers of an engine, and extending along a cylinder line direction; and plural branch passages establishing individual communications between the main passage and corresponding exhaust ports. The respective plural branch passages are so disposed as to be inclined downward from the main passage toward the exhaust ports. Accordingly, it is possible to prevent corrosion of the cylinder head due to stagnation of condensed water.

Abstract: A cooling structure for a cylinder head, wherein the cylinder head has formed therein an exhaust manifold having branch sections and also having a collecting section to which the branch sections connect; a first water jacket and a second water jacket, which cover the exhaust manifold; connection passages which supply cooling water in the second water jacket to the first water jacket; and a cooling water outlet which connects the first water jacket to the outside. The connection passages include the first connection passage which is closest to the collecting section, and the second connection passage which is located at the downstream end of each of the water jackets. The flow passage cross-sectional area of the second connection passage is set to be less than the flow passage cross-sectional area of the first connection passage.

Abstract: A cylinder head with which exhaust manifolds are integrated includes a secondary air supply passage configured to include: a main passage disposed above combustion chambers of an engine, and extending along a cylinder line direction; and plural branch passages establishing individual communications between the main passage and corresponding exhaust ports. The respective plural branch passages are so disposed as to be inclined downward from the main passage toward the exhaust ports. Accordingly, it is possible to prevent corrosion of the cylinder head due to stagnation of condensed water.

Abstract: An oil circulation structure in an internal combustion engine, the oil circulation structure includes a cylinder block and a cylinder head. The cylinder head includes a plurality of exhaust ports. The cylinder head has a plurality of oil holes opened on a surface making contact with the cylinder block. Oil is supplied to the cylinder block through the plurality of oil holes. The plurality of oil holes includes a first oil hole and a second oil hole. The first oil hole is placed further outside an outermost exhaust port in a longitudinal direction of the cylinder block. The second oil hole is placed further outside the first oil hole in the longitudinal direction of the cylinder block, and the second oil hole has a diameter larger than a diameter of the first oil hole.

Abstract: A cooling structure for a cylinder head, wherein the cylinder head has formed therein an exhaust manifold having branch sections and also having a collecting section to which the branch sections connect; a first water jacket and a second water jacket, which cover the exhaust manifold; connection passages which supply cooling water in the second water jacket to the first water jacket; and a cooling water outlet which connects the first water jacket to the outside. The connection passages include the first connection passage which is closest to the collecting section, and the second connection passage which is located at the downstream end of each of the water jackets. The flow passage cross-sectional area of the second connection passage is set to be less than the flow passage cross-sectional area of the first connection passage.

Abstract: A blowby gas ventilation system for a supercharger-equipped internal combustion engine, which discharges blowby gas from a crankcase into intake air, includes a positive crankcase ventilation passage through which the blowby gas is delivered from the crankcase to an intake passage. The positive crankcase ventilation passage branches, in an intermediate location in the positive crankcase ventilation passage, into a first path that is used during natural aspiration of the internal combustion engine and a second path that is used during supercharging of the internal combustion engine, and a part of the positive crankcase ventilation passage, which includes a branching portion between the first path and the second path, is formed integrally with a cylinder head of the internal combustion engine.

Abstract: A cylinder head (1) includes a water jacket (4) formed around an ignition plug mounting hole (5). Upper surfaces (12 to 14) of portions of the water jacket (4) between intake ports (7) and the ignition plug mounting hole (5) and between exhaust ports (8) and the ignition plug mounting hole (5) are set to be lower than upper surfaces (15 to 17) of the remaining portions of the water jacket (4) around the ignition plug mounting hole (5) to increase the rigidity. Thereby, deformation of the cylinder head (1) due to cylinder internal pressure is limited, and the stress concentration around the ignition plug mounting hole (5) due to such deformation is reduced.

Abstract: A cylinder head (1) includes a water jacket (4) formed around an ignition plug mounting hole (5). Upper surfaces (12 to 14) of portions of the water jacket (4) between intake ports (7) and the ignition plug mounting hole (5) and between exhaust ports (8) and the ignition plug mounting hole (5) are set to be lower than upper surfaces (15 to 17) of the remaining portions of the water jacket (4) around the ignition plug mounting hole (5) to increase the rigidity. Thereby, deformation of the cylinder head (1) due to cylinder internal pressure is limited, and the stress concentration around the ignition plug mounting hole (5) due to such deformation is reduced.